Electric lamp



Patented ROBERT S. BUIRNAP,

OF EAST ORANGE, NEW JERSEY, ASSIGNOR T GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC LAMP.

Application filed January 30, 1926. Serial No. 85,010.

% gen or argon.

Certain parts of gas filled incandescent electric lamps and similar devices in which electric current is translated into light, with evolution of heat by an incandescent W filament or by an arc between refractory electrodes, are exposed to currents ofhot gas, and may be heated to dangerously high temperatures. These lamps are usually operated. with the base up, to avoid interference m with downward distribution of the light,

tory material have been mounted on the and, under these conditions, the temperature of the lamp base and the stem seal may become high enough to weaken the base cement and render the glass in the stem seal partially conductive. If direct current is used, electrolysis may occur in the heatedlass of the seal, eventually destroying the ermetical joint between the metal lead and the glass. Discs of mica or similar refracleads or on the cane rod to shield the stem and base, but are difiicult and costly to mount and secure in place. A long'stem, having its inner end enlarged to act as a bafile, has been suggested, but this construction leaves the seal unprotected and so near the filament that, unlessthe lamp is unduly lengthened, the stem is heated to a dangerous temperature.

One object of my invention is to provide a lamp having a stem with integral parts arranged to shield both the lamp base and the stem seal from the currents of hot gas.

Another object is to provide for lamps of this character a stem having protective parts integral with it, yet of such construction that it can easilybe manufactured on automatic machinery substantially like that used for making the stems now in general use.

A further object is to simplify and cheapen the construction of gas filled incandescent lamps and similar devices;

To these ends a tubular stem, made of the stem tubing commonly used, is provided on the inner end with a pocket or recess to trap and hold adjoining the stem seal a quiescent layer of gas which acts as a heat insulator to protect the stem seal from the currents of hot gas from the filament. I may, in addition, provide a radially extending flange integral with the stem and, preferably, on the rim or edge of the This flange may be made by flaring out the inner end of the stem tube, and is of the proper size to protect the base, its rim being preferably adjacent the walls of the bulb, to under the flow of hot gas into the upper end of the lamp. This stem may be manufactured by flaring both ends of a stem tube, and making the press or stem seal for the leads intermediate the ends, instead of' flaring only one end and making the press at the other end, as in making the standard stems now used. The position of the press is such that a portion of the lower end of the stem tube forms the pocket or cup of the same bore as the tube and of suflicient depth, about equal the bore of the pocket, to protect the stem seal.

My invention will best be understood in connection with the accompanying drawing, in which, merely for purposes of illustration, I have shown forms of gas filled lamps embodying my invention, and in which Fig. l.

is a gas filled incandescent lamp; Fig. 2 a form of gas filled arc lamp; Fig. 3 a stem constructed in accordance with my invention, and Fig. 4 a longitudinal section of the stem shown in Fig. 3. Y a

The particular form of gas filled incandescent lamp shown in Fig. 1 comprises a sealed bulb or envelope 1 containing an inert gas, such as nitrogen or argon, and provided with a base 2 of usual construction. The filament 3, preferably of tungsten, is connected to the current supply leads 4, and is carried on anchors secured toa glass rod or arbor 5. In accordance with the usual practice, the arbor 5 is welded or joined at its upper end to the stem seal or press 6, which is a fused mass of glass formed from the walls of the stem tube 7 by pinching together the walls of the tube while hot and plastic. At the same time, the leads 4 and the upper end of the arbor 5 are embedded in this plastic mass or seal. The lamp stem, preferably of the tipless type disclom in pocket.

U. S. patent to Mitchell & White, No. 1,423,956, July 25, 1922, comprises an exhaust tube 8 sealed into the press at the same time as the arbor 5, with a passage through the press formed by air blown into the exhaust tube.

The stem seal or press 6 is protected by a layer or body of substantially quiescent gas trapped and held in the pocket or cup 9 formed by the open lower end of the stem tube, the press 6 constituting the bottom of this on or ocket, the open end of which is above t e fi ament 3 and in the path of the ascending currents of hot gas. This pocket may to advantage have a depth about equal to its bore, and is deep enough to maintain adjoining the stem seal or press 6 a substantially undisturbed layer or body of gas which shields the stem from the currents of hot gas from the filament, so that the seal remains at a safe temperature.

To protect the base, the lower end of the stem tube 7 is provided with a radial flange 10, integral with the stem and large enough to obstruct and divert the upward flow. of hot gas to the vicinity of the base 2, and thereby shield the base to such an extent that it does notattain a dangerously high temperature. The shield maintains a comparatively quiescent body of gas adjoining the based end of the lamp, which acts as a heat insulator. This flange may conveniently be made by flaring the inner end of the stem tube in the same Way as the regular flare 11 for sealing to the bulb is made on the outer end of the stem tube.

A stem constructed in accordance with my invention, as shown in more detail in Figs. 3 and 4, may be made cheaply and with slight modifications of the stem-making machinery now in use. The stem tube is slightly longer than the tube for the stem now commonly used, is flared at both ends instead of at one end only, and'the press or stem seal 6 is located between the ends of the stem tube instead of at its extreme inner end, but these differences are so slight that standard stem-making machinery can, with sli ht modifications, be used to make stems em odying my invention, and at a cost practically no greater than that of the standard stem.

My invention is applicable also to other devices containing hot gases while in operation, such as enclosed arc lamps like that illustrated in Fig. 2, and more fully described in U. S. Patent to Orange, No. 1,279,415, September 17, 1918. This lamp is constructed the same as that shown in Fig. 1, except that the light is obtained-by means of an are between electrodes 12, of tungsten or similar refractory material, mounted by terminal wires 13 on the inner ends of the leads 4. The bulb contains inert atmosphere of nitrogen or argon, in which the arc operates. The

stem seal and the base are protected from the hot gases by the same construction of stem as that lamp shown in Fig. 1.

\Vhat I claim as new, and desire to secure by Letters Patent of the United States, is:

1. A sealed envelope containing gas, and having a re-entrant tubular portion with'its inner end open to the interior of said envelope and closed at a point remote from said inner end, to form a tubular pocket of substantially the same bore as the remainder of said tubular portion, leads sealed into the bottom of said pocket to project therefrom, and means on the projecting ends of said leads for translating electrical energy with evolution of heat.

2. A sealed envelope containing gas, a stem tube projecting into said envelope, 0. press or seal intermediate its ends and sufliciently remote from the inner end of the tube to form a pocket of a depth about equal to the bore of the pocket, leads hermetically sealed into said press, to project beyond said inner end into the interior of said envelope, and means on the inner end of said leads translating electrical energy with evolution of heat.

3. A sealed envelope containin as, and having an inwardly projecting tu u ar stem with its inner end flared into an integral radial flange, leads mounted inside said stem, to project inwardly beyond said flange, and hermetically sealed into said stem at a point remote from said flange, whereb the inner tubular portion of said stem orms about said leads a pocket of substantially the bore and depth of the bore of the stem, and a filament secured to the inner ends of said leads.

4. A sealed bulb containing gas, a tubular stem having its outer end flared and sealed to the neck of the bulb and its inner end flared into an integral radial flange, an arbor concentric with and smaller than the bore of said stem and joined at its end to a mass of glass, which closes said stem at a point intermediate its ends and sufiiciently remote from its inner end to form a pocket of substantially the same bore and depth as the bore of said stem, leads extending through said stem tube and hermetically sealed into said mass of glass, and a filament on the inner ends of said leads.

5. A sealed bulb containing gas, a tubular stem flared at its outer end and sealed to the neck of the bulb and flared at its inner end into an integral flange, said tube being closed by a press of fused glass at a oint intermediate its ends whereby the tu ular inner end becomes a pocket of a de th substantially the same as the bore of said stem, leads hermetically sealed into said press to extend beyond the inner end of said stem, an arbor smaller than the bore of said stem and joined at one end to said press to project into said bulb, and a filament supported by said arbor and connected to said leads.

6. A lamp stem comprising a tube flared at both ends and closed intermediate its ends by a fused mass of glass to form on its inner end a pocket of a depth at least equal to the bore of said steni, and a lead smaller than the bore of said tube embedded in said mass to extend beyond one flared end of said tube.

7 A lamp stem comprising a pair of leads, and a mass of glass in which said leads are embedded and having a tubular portion which has its free end flared into an integral radial flange and which extends along the leads to form a pocket of substantially the 15 same depth as the bore of said pocket around them; In Witness whereof, I have hereunto set my hand this 28th day of January, 1926.

ROBERT S. BURNAP. 

